System for cooling components in an electronic module

ABSTRACT

A device is provided that includes a heat conductive structure; a heat transfer structure for extracting heat from the heat conductive structure by means of a boundary layer; a motor for rotating the heat transfer structure relative to the heat conductive structure; and a vertical fixing mechanism for allowing the heat transfer structure to rotate above the heat conductive structure without making contact with the heat conductive structure so as to define a boundary layer between the heat conductive structure and heat transfer structure, wherein the heat transfer structure extracts heat from the heat conductive structure by means of the boundary layer, and wherein the heat conductive structure includes small geometric turbulators.

BACKGROUND

The present device generally relates to a system for cooling componentsin an electronic module.

In the challenge for miniaturization, small but powerful devices developthis severe cooling requirement: increasing currents in smallerelectronic devices increment heat confinement (^(˜)200 W/cm²) and affectthe electronic devices' overall performances to the limit of reducingefficiency performance, damaging the device, and producing systemoverheating with risk of fire hazard.

Reduction of thermal resistance for a given heat power concentration isa challenging topic. There is the opportunity in the art for a moreefficient heat management system either incrementing airflow (reductionof heat sink resistance) and improving heat transfer from a heat sourceto a heat sink, while maintaining low cost of product and process as adriving objective.

The traditional approach for cooling an electronic module is using aheat sink and a fan as shown in FIG. 4A where the heat sink 1 is made ofa highly thermal conductive material having narrow channels in which acoolant fluid is forced to pass by the fan 2. Heat must be transferredfrom a heat source 3 (to which thermal loads are fixed) to the rotatingimpeller 4 of the fan 2 by transferring heat from the heat source 3 tothe heat sink 2 to the impeller 4 by a coolant filled gap 5 (gas bearingor air bearing). The working point of this system generally requires thesolution of conjugated transfer between solid and fluid (Biot numbernear one). This situation poses different issues from the reduction ofhydraulic resistance to maximization of heat exchange.

SUMMARY

According to one aspect of the present invention, a device is providedcomprising: a heat conductive structure having a first surface; arotating heat transfer structure for extracting heat from the heatconductive structure by means of a boundary layer that contacts thefirst surface of the heat conductive structure; a motor for rotating theheat transfer structure relative to the heat conductive structure; and avertical fixing mechanism for allowing the rotating heat transferstructure to rotate above the heat conductive structure without makingcontact with the heat conductive structure so as to define a boundarylayer between the heat conductive structure and rotating heat transferstructure, wherein the rotating heat transfer structure extracts heatfrom the heat conductive structure by means of the boundary layer, andwherein the first surface of the heat conductive structure includesturbulators to promote the instability of vorticity forming in theturbulators by resonant mechanism.

According to another aspect of the present invention, an apparatus isprovided comprising: a thermal reservoir; a rotating heat transferstructure having an axially symmetrical body made of a conductivematerial with fins for transferring fluid from in an inlet port to anoutlet port; a motor for rotating the rotating heat transfer structurerelative to the heat sink; and a Belleville spring assembly bearing theinertial forces acting on the rotating heat transfer structure whileallowing precise setting of the distance of the rotating heat transferstructure with respect to the thermal reservoir such that there is nocontact between the rotating heat transfer structure and the thermalreservoir, the Belleville spring assembly comprising multiple sets ofBelleville springs assembled on both sides of the rotating heat transferstructure to set the displacement by leverage nut displacement.

According to another aspect of the present invention, an apparatus isprovided comprising: a thermal reservoir; a rotating heat transferstructure having an axially symmetrical body made of a conductivematerial with fins for transferring fluid from in an inlet port to anoutlet port; a motor for rotating the rotating heat transfer structurerelative to the heat sink; and a differential screw mechanism bearingthe inertial forces acting on the rotating heat transfer structure whileallowing precise setting of the distance of the rotating heat transferstructure with respect to the thermal reservoir such that there is nocontact between the rotating heat transfer structure and the thermalreservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the detaileddescription and the accompanying drawings, wherein:

FIG. 1A is a side elevational view of a turbo rotating heat sinkaccording to a first embodiment;

FIG. 1B is an exploded perspective view of the turbo rotating heat sinkof FIG. 1A;

FIG. 2A is a side elevational view of a portion of the turbo rotatingheat sink of FIG. 1A;

FIG. 2B is a plan view of a rotating heat transfer structure of theturbo rotating heat sink of FIG. 1A;

FIG. 3 is a flow chart of a method of assembly of the turbo rotatingheat sink of FIG. 1A;

FIG. 4A is a side elevational view of a prior art heat sink;

FIG. 4B is a side elevational view of the turbo rotating heat sink ofFIG. 1A shown with a heat source;

FIG. 5 is a graph of gap height design values in microns as a functionof power concentration and temperature difference;

FIG. 6 is a side elevational view of a first version of the turborotating heat sink of FIG. 1A;

FIG. 7 is a graph showing Belleville springs nonlinear behavior for fineadjustment of gap height;

FIG. 8 is a side elevational view of a second version of the turborotating heat sink of FIG. 1A;

FIG. 9 is a close up view of the portion of FIG. 8 identified as IX;

FIG. 10 is a side elevational view of a rotating heat sink according toa second embodiment;

FIG. 11 is an exploded perspective view of the rotating heat sink ofFIG. 10;

FIG. 12 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 13 is an illustration of turbulence of flow instability of thewhirls as promoted by resonance by secondary flows of the streamlinedflow of FIG. 12 and the turbulators of the rotating heat sink of FIG.10;

FIG. 14 is a graph of the relationship between the Strouhal numberversus the Reynolds number;

FIG. 15 is a side elevational view of a first version of the rotatingheat sink of FIG. 10;

FIG. 16 is a side elevational view of a second version of the rotatingheat sink of FIG. 10;

FIG. 17 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 18 is a cross-sectional view of the heat conductive structure shownin FIG. 17 as taken along line XVIII;

FIG. 19 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 20 is a cross-sectional view of the heat conductive structure shownin FIGS. 19, 21, and 22 as taken along line XX;

FIG. 21 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 22 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 23 is a plan view of a heat conductive structure of the rotatingheat sink of FIG. 10;

FIG. 24 is a cross-sectional view of the heat conductive structure shownin FIG. 23 as taken along line XXIV; and

FIG. 25 is a plot of the relation of δ as a function of λ, Reh.

DETAILED DESCRIPTION OF EMBODIMENTS

For purposes of description herein the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the device as oriented in FIG. 1. However, it isto be understood that the device may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

Some of the embodiments described herein relate to a turbo rotating heatsink in which a fan and a heat sink are integrated in a rotating heattransfer structure such as an impeller. The turbo rotating heat sink maybe used to flush fluid thereby extracting heat from integrated circuitelectronics, solid state and integrated devices such as CPUs and GPUs,amplifiers, and transistors. The convective heat transfer is largelyaugmented by the high speed of the fluid blowing between rotating vanesof blades (fins).

Referring to the embodiment illustrated in FIG. 1A, a turbo rotatingheat sink 10 is shown having a rotating heat transfer structure 12 (suchas an impeller or a rotating disk), which has an axis-symmetrical bodymade of a thermally conductive material with fins 14 for pumping a fluidfrom an inlet to an outlet port. The turbo rotating heat sink 10 furtherincludes a motor 20 for rotating the heat transfer structure 12 toprovide a pressure head between the inlet port 34 and outlet port 36 ofa volute 30 (FIG. 1B). Additionally, the turbo rotating heat sink 10 mayinclude a mechanical system 40 bearing the inertial forces acting on therotating heat transfer structure 12 thereby allowing precise setting ofthe distance of the rotating heat transfer structure 12 with respect toa thermal reservoir 50 without solid contact with the rotating heattransfer structure 12.

The mechanical system 40 sets the distance h_gap between the rotatingheat transfer structure 12 of diameter D and the thermal reservoir 50 inthe range of 2.5e-4 times D and 5e-3 times D. The motor 20 may be fixedto the mechanical system 40 in proximity of the inlet port 34.

A volute 30 or an encasing is provided for supporting the pressure headtwo fluid ports (inlet port 34 and outlet port 36) and confining theflow between different pressures. Such a volute 30 may be fixed tothermal reservoir 50. An example of the volute 30 and other componentsof the turbo rotating heat sink are shown in FIG. 1B. The volute 30 isprovided with oriented fins 32. The fins 32 may be located at the inletport 34 to orient the flow thereby reducing fluid speed and increasingthe pressure head.

As shown in FIG. 1B, a shaft 54 having Belleville springs 40 a or thelike, may be attached to the thermal reservoir 50 and a bearing 52 maybe slid over the shaft 54 for securing the rotating heat transferstructure 12. The motor 20 and the mechanical system 40, which may beanother Belleville spring as discussed below, are also slid onto theshaft 54. The volute 30 may then be slid over the shaft 54.

As noted above, the rotating heat transfer structure 12 (also referredto herein as the “impeller”) is provided with fins 14 or similarstructures such that the fluid sections are provided relative to thevolute 30. The fins 14 may be tapered along the stream direction h(s)(FIG. 2A), which reduces departing from rotation axis according to therelation h(s)*r(s)<=Const, with r(s) being the distance from rotationaxis of the given section along flow meridional coordinate s.

The thickness t(r) of the body of the rotating heat transfer structure12 reduces from the center to the maximal diameter according to thefunction t(r)*(1+a r{circumflex over ( )}2)<diameter*0.3, where r is theradial coordinate (r<impeller diameter/2), and a is a constant in therange of 0 to 1.

FIG. 2B shows a top view of the rotating heat transfer structure 12. Asshown, the fins 14 are curved with respect to a radius of the structure.

As a turbo-machine, the profile and the height of the fins is designedto avoid recirculation in the presence of an adverse pressure head. Theheight H(r) of the fins 14 may be h(r(s))*r<diameter{circumflex over( )}2*0.2).

The encasing or volute 30 is configured such that the volute ishydraulically connected with the volume confined between given rotatingheat transfer structure 12 and thermal reservoir 50.

The embodiments now described below provide a benefit of an absence ofany gap control mechanism. Two embodiments described herein adjust thegap height or distance between the rotating heat transfer structure 12and the fixed thermal reservoir 50 during the assembly procedure.

The mechanical system 40 may precisely allow for the assembly of themating surfaces while allowing for relative rotation of the rotatingheat transfer structure 12. Both gap adjustment solutions share theobjective of zeroing the stack-up uncertainty due to parts' tolerances,while bearing the pressure and inertial forces acting on the rotatingheat transfer structure 12. The gap height adjustment reduces gap heightto a design value reducing the risk of galling during high temperatureand thermal load conditions.

The method of assembling the turbo rotating heat sink 10 is describedbelow with reference to FIG. 3. First, a motor 20, rotating heattransfer structure (impeller) 12, and a bearing/bushing 52/shaft 54subassembly are provided and are assembled on a reference frame (step100) while maintaining both a shaft 54 reference and an impeller/basemating surface reference. Specifically, a ball or sleeve bearing 52 isassembled to the rotating heat transfer structure 12 using the referenceframe, and then the shaft 54 is assembled to the rotating heat transferstructure 12 with free relative rotation. The motor 20 is then tested byinducing rotation on the rotating heat transfer structure 12 and in step102 it is determined whether the rotating heat transfer structure 12 isdynamically and statically balanced to allow free spinning. If not, step100 is repeated by re-assembling the parts on the reference frame.Otherwise, step 104 is performed to assembly the mechanical system 40 tothe motor 20 and shaft 54 to form a preassembled impeller 106.Preassembled impeller 106 is mounted on the baseplate (thermal reservoir50) while the rotating heat transfer structure 12 is freely rotating instep 108. The shaft 54 is screwed in the baseplate and the firstfrictional contact between the rotating heat transfer structure andbaseplate starts braking the rotating heat transfer structure rotation.If there is no such braking, the shaft 54 is further screwed into thebaseplate. Otherwise, if there is braking, which can be sensed bynoise/friction or a sharp reduction of rotation, the gap height isadjusted in step 112 to the design value. Specifically, the gap heightmay then set from zero (starting contact between parts) to the designheight (i.e., 30 μm, 100 mm in diameter, max load 300 W, max operationaltemperature 40° C.) from design graph (FIG. 5) to avoid any risk ofimpeller galling in consequence of thermal load or temperatureincrement. FIG. 5 shows gap height design values in microns as afunction of power concentration and temperature difference (source toair) to avoid impeller galling due to different thermal dilation (steelshaft and aluminum/copper bodies).

Different factors interact in these embodiments to provide variousbenefits. These factors include: encumbrance (i.e. impeller diameter);precise machining and assembly of mating surfaces with a flatnessvariance of 0.02 mm or less over 100 mm of diameter; gap heightexceeding the planarity and roughness of mating surfaces; given airproperties, the gap thermal resistance is reduced below 3.75E-05 m²/μmK/W: i.e. for a gap of 40 μm (corresponding to a flatness of 0.02 mm)for a surface of 1E-2 m², Rthermo=3.75E-05 m²/μm K/W*40 μm/1E-2 m₂=0.15K/W; convective transfer between air and the rotating heat transferstructure 12 increases with rotation speed; pressure in the air gapincreases with rotation speed; for passive controlled gap controls, thegap height increment with pressure and rotation speed results in anincrement of thermal resistance in the gap; air bearing creation (byhydrodynamic features) and control (preloaded spring or counter airbearing) affect thermal performance; and in case of passive control ofgap height (preload counter spring), the take-off speed and the rotationspeed for minimal overall thermal resistance are linked.

As mentioned above, there are two solutions described below pertainingto the mechanical system 40. Both solutions share the objective ofzeroing stack-up uncertainty due to parts' tolerances, while bearing thepressure and inertial forces acting on the rotating heat transferstructure 12.

The first solution is shown in FIG. 6 and includes a spring settingmechanism 140 used as the mechanical system 40. The shaft 54 allows forassembly of rotating heat transfer structure 12 with respect to themating surface of the thermal reservoir 50. The spring setting mechanism140 includes a plurality of Belleville springs 142 and 144 positionedabove and below rotating heat transfer structure 12. From thisconstruction, the Belleville spring setting mechanism 140 allows precisesetting of the distance of the rotating heat transfer structure 12 fromthermal reservoir 50 by adjusting the spring stiffness of the Bellevillesprings 142 and 144. Note that the bearing 52 is allowed to slide on theshaft but not tilt.

Belleville springs 142 and 144 provide the support force against theweight of the rotating heat transfer structure 12 and the air bearingforces. The Belleville springs 142 and 144 preload exceeds by far theweight of the rotating heat transfer structure 12. The assembly ofsoftening Belleville springs 142 and 144 (decreasing spring stiffness)allows for precise setting of the relative position of the rotating heattransfer structure 12. As described above with respect to FIG. 3, theshaft 54 is screwed in the thermal reservoir 50 using a referencecylinder until the first contact between rotating heat transferstructure 12 is detected, and from this fixed position, a springretaining nut 146 is unscrewed to allow the precise setting of the gapat a minimum level. When the Belleville springs 142 and 144 arepreloaded in the nonlinear range of the displacement, unscrewing of thespring retaining nut 146 is almost completely absorbed by the upperBelleville spring 142, thus allowing for precise setting of distance(see the graph of displacement in FIG. 7). FIG. 7 shows the Bellevillenonlinear stiffness characteristic that allows sub-micron accuracyadjustment of the gap. In FIG. 7, the vertical axis is thenon-dimensional compression force acting on the Belleville springs 142and 144. The Belleville springs 142 between the bearing 52 and thespring retaining nut 146 show a reduced nonlinear stiffness (softeningcharacteristic) with respect to the Belleville springs 144 between thebearing 52 and the thermal reservoir 50. This assembly of the Bellevillesprings 142 and 144 allows for fine adjustment of the gap position sincesoftening springs withstand most of the displacement of the regulatingnut.

Once assembled, the preload of the Belleville springs 142 and 144 firmlyholds the rotating heat transfer structure 12 against the inertialforces to prevent solid contact between the rotating heat transferstructure 12 and thermal reservoir 50 (baseplate) at any rotation speed.

The second solution is shown in FIGS. 8 and 9 and uses a differentialscrew 240 as the mechanical system 40. At every turn of the differentialscrew 240, the gap height reduces by the difference between the twothread pitches.

The rotating heat transfer structure 12 and the thermal reservoir 50 arenot in contact after assembly. A retaining nut 242 allows fordifferential control of the gap height. The gap height is not affectedby rotation speed and the differential screw 240 corrects the tolerancesreducing the gap height to the minimum value (i.e., 2.5E-4 times D, thediameter of rotating heat transfer structure).

Benefits of the embodiments shown in FIGS. 1A-9 are:

-   -   the absence of any control mechanism: two solutions are        disclosed to set the distance between the rotating heat transfer        structure 12 and fixed thermal reservoir 50;    -   the electric motor 20 is placed away from the thermal reservoir        50 in a cooler zone (see FIG. 4B versus FIG. 4A) and due to        this, the operating temperature of the system can be increased,        thereby increasing heat dissipation;    -   the motor 20 is inserted upon the rotating heat transfer        structure 12 in a central hub and the higher thickness of the        body of the rotating heat transfer structure 12 allows for a        natural flowing of heat from the center to the periphery of the        rotating heat transfer structure 12;    -   the heat exchange area between the thermal reservoir 50 and the        rotating heat transfer structure 12 is increased due to the        absence of the motor 20 between them;    -   the absence of solid contact between the thermal reservoir 50        and the rotating heat transfer structure 12 (at start up);    -   the absence of a take-off speed for the rotation of the rotating        heat transfer structure 12 with a broad range of allowed        rotation speed;    -   a sharp reduction of motor 20 requirements allowing higher        rotation speed;    -   the absence of rotation speed incidence over gap height;    -   precise setting of gap height within precision of the mating        surfaces;    -   the ability of holding of the pressure head in the presence of        hydraulic resistance demands a high speed of the flow in the        outlet section of the rotating flow: the flow section h(s)        should therefore reduce moving radially from the rotation axis        (this reduces the stall in presence of counter pressure);    -   limited machining of the mating parts with reduced constraints        over mating surface planarity;    -   impeller (rotating heat transfer structure 12) stiffness is        increased in consequence of the reduction of section area t(r)        of the rotating heat transfer structure 12; and    -   impeller thickness reduces radially (t(r)): impeller stiffness        to centrifugal forces reduces embossment of impeller centrifugal        forces and the reduction in thickness facilitates thermal flux        from the center to the periphery of the rotating heat transfer        structure 12.

Another embodiment is described below with reference to FIGS. 10-25. Asystem for cooling the components in an electronic module is disclosed.As shown in FIGS. 10 and 11, the cooling system 300 of the presentinvention comprises a rotating heat transfer structure (rotating thindisk) 312 fixed with the rotating axis to a heat conductive structure350 (i.e., thermal reservoir) attached to a heat source 352. Therotating heat transfer structure 312 is driven by an electric motor 20.The rotating heat transfer structure 312 rotates on the heat conductivestructure 350 and remains separated from it by a thin layer of air (airgap).

In consequence of the rotation of the rotating heat transfer structure312, the surrounding air enters the air gap with a spiraling motion (seeFIG. 12) and exits the air gap in consequence of the unbalance ofinertial force (Taylor Görtler secondary flows: centrifugal force onrotating heat transfer structure exceeds centrifugal force on fixeddisk). This net flux can be ducted to extract heat from fixed heatconductive structure 350 added with small geometrical featureshereinafter referred to as ‘turbulators’ 356 (local vortexes form andare blown away) with the secondary flow already described.

The turbulators 356 are added to a heat transfer enhanced surface 354 ofheat conductive structure 350 to improve the convective heat transferwithin the air gap; these turbulators 356 are based on a geometry topromote transition from laminar to turbulent flow, analogous to dimpleson golf balls. Specifically the grooves/dimples forming the turbulators356 are designed to generate blown away vortex structures resonatingwithin the spiraling flow in the air gap due to the rotating heattransfer structure 312 (see FIGS. 10 and 12). The turbulator 356geometry is based on a groove/dimple geometric nondimensional parameterδ, as a function of the gap height h, disk diameter ϕ and the volume/wetsurface of dimple d as described further below.

As shown in FIG. 13, a resonating condition is obtained by defining thedistance Lc along the streamline direction to resonate the vorticity inone dimple to the successive dimple according to Strouhal correlation.FIG. 14 shows a plot of the Strouhal number versus Reynolds number forcircular cylinders (tubes). From Blevins R. D. (1990) Flow InducedVibrations, Van Nostrand Reinhold Co. Note that Strouhal number(nondimensional frequency) becomes almost independent from Reynoldsnumber when it exceeds 1E2. As shown in FIG. 12, the imposed rotation ofdisk causes a spiraling shape of the streamline. Small δ dimensions arenucleation sites for vorticity. The vorticity field enters the resonantmode promoting the detachments of eddies (as depicted in FIG. 13) forgiven Lc/ϕ/δ values. Note that give azimuthal-cyclic symmetry thecomputational domain for the system can be properly reduced.

The advantages of the system include, but are not limited to, the ultralow profile, the high heat dissipation performance related to the formfactor, and a low noise level. The introduction of an ultra low profilerotating cooler has the potential to simplify the problem ofencumbrance, cooling air ducting and air blowing. The forced convection,and heat transfer enhancement is a consequence of correct design of thefluid dynamics of the cooling air within the air gap.

Unlike prior designs, the heat transfer from the heat conductivestructure 350 is directly solved by the vortex flow (flow spiralling)inside the air gap formed by the rotating heat transfer structure 312.The rotating heat transfer structure 312 or “impeller” can be free fromfins, blades or vanes. Nevertheless, the rotating heat transferstructure 312 may have a construction such as shown above in the firstembodiment. In this proposed apparatus the air gap is used as the mainmechanism to promote the thermal exchange.

Two variations of this embodiment are disclosed, with the firstvariation shown in FIG. 15 and the second variation shown in FIG. 16. InFIG. 15, the first variation includes a rotating heat transfer structure312 for pumping out heat from a heat conductive structure 350, a motor20 rotating the rotating heat transfer structure 312, and a shaft andair gap control mechanism 340. In the second variation shown in FIG. 16,the construction is the same with the exception that the rotating heattransfer structure 312 includes an inlet port 314 in the central portionof the rotating heat transfer structure (Tesla turbine) allowing airflow from the internal zone of the air gap.

The air gap (mentioned as region sandwiched between said fixed heatconducting structure and said rotating heat transfer structure) providesthe heat transfer a true fluid media (with relative thermal resistance)between the heat conductive structure 350 and the rotating heat transferstructure 312. For correct operation of the system, the air gap ismaintained within design specifications. Specifically, as mentionedabove, the turbulator 356 geometry is based on a groove/dimple geometricnondimensional parameter δ, as a function of the gap height h, diskdiameter ϕ and the volume/wet surface of dimple d. The design parametersbeing:

h average gap [m] Φ disk diameter [m] v fluid kinematic viscosity[0.6-5E−5 m2/s] ω rotation speed [Hz = s − 1] d volume/wet surface ofdimple [m] Lc mean distance of “dimples” in streamline direction [m]

Two nondimensional groups are defined:

Reh = hΦω/v Gap height rotational Reynolds number λ = h/Φ Geometric nondimensional parameter δ = d/(λΦ) Groove/dimple geometric non dimensionalparameter

The design constrains herein disclosed are:

-   -   λ<5E-3 (“thin gap”)    -   Reh<1E2 (“limited speed”: i.e. ϕ=1E-1m in air ω<5E2 Hz)    -   δ<1E1 (“limited dimple dimension”)    -   1E-2<Lc/ϕ<1E-1 (“limited number of dimples”)    -   1E1 δ<Lc/ϕ<1E-1 δ (“dimple resonant condition”)

Different kinds of turbulators 356 (grooves/dimples) are proposed topromote thermal extraction from the heat conductive structure 350 andare shown in FIGS. 17-24. The turbulator designs shown in FIGS. 19-22are low profile features obtained by EDM or machining (0.02-0.8 mm indepth). The turbulator design shown in FIGS. 17 and 18 has ultra lowprofile features obtained by stamp marking or EDM. The turbulator designshown in FIGS. 23 and 24 has a geometry obtained to increase 8 linearlyalong radial direction (dimples).

The indicative dimension of dimples in δ*1E2 at different Reh and A thatallows for resonant mechanism is shown in the graph of FIG. 25.

The ultra low profile rotating cooler shown in FIGS. 10-24 introducesbenefits in terms of:

-   -   ultra low encumbrance in vertical direction;    -   absence of contact between rotating heat transfer structure and        heat    -   conductive structure (fixed disk);    -   effective heat transfer in the air gap;    -   reducing thermal resistance with gap height and rotation;    -   disk material can be conductive and nonconductive;    -   simplified assembly and stack up of the elements; and    -   no complex machining of the parts (low cost).

It will be understood by one having ordinary skill in the art thatconstruction of the described device and other components is not limitedto any specific material. Other exemplary embodiments of the devicedisclosed herein may be formed from a wide variety of materials, unlessdescribed otherwise herein.

For purposes of this disclosure, the term “coupled” (in all of itsforms, couple, coupling, coupled, etc.) generally means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents. Such joining may be permanent in nature or may be removableor releasable in nature unless otherwise stated.

It is also important to note that the construction and arrangement ofthe elements of the device as shown in the exemplary embodiments isillustrative only. Although only a few embodiments of the presentinnovations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements shown as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures and/or members or connector or otherelements of the system may be varied, the nature or number of adjustmentpositions provided between the elements may be varied. It should benoted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present innovations.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the desired andother exemplary embodiments without departing from the spirit of thepresent innovations.

It will be understood that any described processes or steps withindescribed processes may be combined with other disclosed processes orsteps to form structures within the scope of the present device. Theexemplary structures and processes disclosed herein are for illustrativepurposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can bemade on the aforementioned structures and methods without departing fromthe concepts of the present device, and further it is to be understoodthat such concepts are intended to be covered by the following claimsunless these claims by their language expressly state otherwise.

The above description is considered that of the illustrated embodimentsonly. Modifications of the device will occur to those skilled in the artand to those who make or use the device. Therefore, it is understoodthat the embodiments shown in the drawings and described above is merelyfor illustrative purposes and not intended to limit the scope of thedevice, which is defined by the following claims as interpretedaccording to the principles of patent law, including the Doctrine ofEquivalents.

What is claimed is:
 1. A device comprising: a heat conductive structurehaving a first surface; a rotating heat transfer structure forextracting heat from the heat conductive structure by means of aboundary layer that contacts the first surface of the heat conductivestructure; a motor for rotating the heat transfer structure relative tothe heat conductive structure; and a vertical fixing mechanism forallowing the rotating heat transfer structure to rotate above the heatconductive structure without making contact with the heat conductivestructure so as to define the boundary layer between the heat conductivestructure and rotating heat transfer structure, wherein the rotatingheat transfer structure extracts heat from the heat conductive structureby means of the boundary layer, wherein the first surface of the heatconductive structure includes turbulators to promote the instability ofvorticity forming in the turbulators by resonant mechanism, and whereinthe vertical fixing mechanism is a differential screw mechanism bearingthe inertial forces acting on the rotating heat transfer structure whileallowing precise setting of the distance of the rotating heat transferstructure with respect to the thermal reservoir such that the distanceis not affected by rotation speed.
 2. The device of claim 1, wherein therotating heat transfer structure is a rotating disk.
 3. The device ofclaim 1, wherein the turbulators are configured to have a geometricnondimensional parameter λ<5E-3, where λ=h/Φ, h is the average gapheight between the heat conductive structure and the rotating heattransfer structure, and Φ is the diameter of the rotating heat transferstructure.
 4. The device of claim 1, wherein the device exhibits a gapheight rotational Reynolds number Reh<1E2, where Reh=hΦω/v, h is theaverage gap height between the heat conductive structure and therotating heat transfer structure, Φ is the diameter of the rotating heattransfer structure, ω is the rotation speed of the rotating heattransfer structure, and v is the fluid kinematic viscosity.
 5. Thedevice of claim 1, wherein the turbulators are configured to have ageometric nondimensional parameter δ<1E1, where δ=d/(λΦ), d is thevolume/wet surface of each turbulator, λ is a geometric nondimensionalparameter that is equal to λ=h/Φ, h is the average gap height betweenthe heat conductive structure and the rotating heat transfer structure,and Φ is the diameter of the rotating heat transfer structure.
 6. Thedevice of claim 1, wherein the turbulators are limited in number to1E-2<Lc/Φ<1E-1, where Lc is the mean distance of turbulators in astreamline direction, and Φ is the diameter of the rotating heattransfer structure.
 7. The device of claim 1, wherein the deviceexhibits a dimple resonant condition of 1E1 δ<Lc/Φ<1E-1 δ, where Lc isthe mean distance of turbulators in a streamline direction, δ=d/(λΦ), dis the volume/wet surface of each turbulator, λ is a geometricnondimensional parameter that is equal to λ=h/Φ, h is the average gapheight between the heat conductive structure and the rotating heattransfer structure, and Φ is the diameter of the rotating heat transferstructure.
 8. The device of claim 1, wherein the rotating heat transferstructure includes an inlet port in a central portion of the rotatingheat transfer structure allowing air flow therethrough to the boundarylayer.
 9. An apparatus comprising: a thermal reservoir; a rotating heattransfer structure having an axially symmetrical body made of aconductive material with fins for transferring fluid from an inlet portto an outlet port; a motor for rotating the rotating heat transferstructure relative to the heat sink; and a differential screw mechanismbearing the inertial forces acting on the rotating heat transferstructure while allowing precise setting of the distance of the rotatingheat transfer structure with respect to the thermal reservoir such thatthere is no contact between the rotating heat transfer structure and thethermal reservoir, the differential screw mechanism configured such thatthe distance of the rotating heat transfer structure with respect to thethermal reservoir is not affected by rotation speed of the rotating heattransfer structure.
 10. The apparatus of claim 9 and further comprisinga volute fixed to the thermal reservoir for supporting a pressure headbetween two fluid ports and confining fluid flow between differentpressures.
 11. The apparatus of claim 10, wherein the volute includesoriented fins at an intake section to orient fluid flow and therebyreduce fluid speed and increase the pressure head.
 12. The apparatus ofclaim 9, wherein the rotating heat transfer structure includes aplurality of fins that are tapered along a radial direction such thatthe height of the fins h(s) reduces from rotation axis towards theperiphery of the rotating heat transfer structure according to therelation h(s)*r(s)<=Const, where r(s) is the distance from rotation axisalong a flow meridional coordinates.
 13. The apparatus of claim 9,wherein the rotating heat transfer structure includes a body thatreduces in thickness t(r) from the center to the maximal diameter, wherer is the radial coordinate (r<diameter/2) with a decreasing function ofthe radius r(s).